In the manufacture of game balls such as baseballs, softballs and the like, it is well known to make a core, and cover the core with a material to provide the necessary strength and resilience, followed by an outer, leather cover. The preformed cores have typically been made of a wide variety of materials, two of the most popular cores being kapok and cork. It will be recognized, of course, that each of these materials has insufficient strength to act as a game ball; therefore, an intermediate material, such as windings of string or yarn, is normally placed over the preformed core to give the ball the required strength, resilience and sound when hit with a bat. The finished winding or other material receives a conventional cover thereover so the completed ball will be the predetermined size in accordance with the game to be played.
There has long been considerable difficulty with the prior art balls made with the preformed core, the winding and the leather cover. First, the strength of the ball is simply insufficient for the ball to withstand for very long the extremely large forces involved in a baseball game. It is not uncommon for a baseball to have a playable life shorter than one baseball game simply because the cover will split, the windings will break, and the core will become sufficiently non-spherical that the ball will not have the proper handling and flight characteristics. Additionally, it will be understood that string, kapok, cork and the like will absorb moisture so that, if the ball becomes wet, the weight of the ball will be tremendously increased and the strength of the ball will be decreased. Once the ball is wet, the ball will deform rather easily, so the ball is not acceptable in a conventional baseball or softball game.
With the vast technology in plastic materials, there have been several balls formed of foamed plastics. These have taken the form of a molded sphere of expanded plastic material, the sphere being covered by the conventional leather cover, with or without an intermediate winding of string. These balls also have not met with great success. In some balls, the coefficient of restitution of the ball is too great, which is to say the ball rebounds better than is desired. When hit by a baseball bat, such a ball travels so fast as to be a distinct danger to players. Also, when some plastic balls are cold, they become so dense as to bend a metal bat. A ball has been made of a cross-linked polyurethane, and this ball has been found to be affected by changes in climate so that the ball is not consistent. Also, the polyurethane ball tends to take a compression set, so the sphericity is not guaranteed during play. Furthermore, the game ball industry has an investment in manufacturing facilities for making the preformed core for a game ball, so it is desirable to retain the preformed core, yet to improve the ball to overcome the above mentioned difficulties and to make a ball that meets current demands for a game ball. While some of the previous plastic balls rebound too greatly, it is desired to have a ball with a somewhat greater coefficient of restitution than the conventional cork and string ball, and to have the desired sharp sound when the ball is hit with a bat.